Photochromic organic compounds for optical memory

Abstract

For the purpose of target syntheses of new photochromic compounds, a relationship between the structure and properties of a series of the known thermally irreversible photochromes was analyzed using the spectral kinetic data obtained by the authors.Progress in information technologies demands a sharp increase in the informational capacity of information carriers and in the rate of data processing.An analysis of the modern state of research in this area 1 shows that the limiting density of information re cording on magnetic discs can reach 230 Gbit inch -2 . In this case, the informational capacity of magnetic discs can be increased to 20 Gbit. The rate of data processing can be 1 Gbit s -1 .In addition to magnetic discs, optical discs (ODs) for archive storage of information are widely popular. They can be of the CD type (type I), providing multiple read ing of an optical information recorded in a studio, and of the WORM type (type II) with a single recording and multiple reading directly in a personal computer. Rever sive ODs of the WERM type (type III) were created for operative multiple recording and repeated recording of optical information and its multiple reading. Optical in formation recording on the most part of known ODs is based on thermoinduced processes of substance conver sion. In the case of ODs of types I and II, information recording is performed due to the thermoinduced abla tion of deposited in vacuo layers of organic and inorganic substances. Reversible recording -rewriting of optical information in an OD of type III occurs due to the ther moinduced magnetization reversal of magnetic domains in optical discs or reversible phase transformations of metallic alloys. The informational capacity of these ODs used for information reading from a semiconducting la ser with a radiation wavelength of 650 nm is ~4.7 Gbit. New commercial ODs developed by the Blu ray Disc Association have the record breaking informational ca pacity: 25 Gbit for single sided and 50 Gbit for double sided (DVD) information carriers, which is achieved by the application of a semiconducting laser with a shorter wavelength (405 nm), an optical system with a digital aper ture of 0.7/0.8, and the photosensitive layer with a thickness of 0.1 mm.Prospects for increasing the informational capacity of ODs are related to the creation of multilayer photosensi tive coatings for bitwise information detection and thick (>2 mm) photosensitive layers for holographic informa tion detection. These ODs provide the three dimension al (3D) optical memory with the recording density higher than 1 Tbit due to information recording and reproduc tion in various layers of a detecting medium (in the case of the bitwise optical memory) or at different incident angles of the activating and recovering laser radiation (in the case of the holographic optical memory).The prospects for improving ODs for optical memory are associated with the use of photosensitive organic me dia that experience photochemical transformations. In principle, these media possess a hi...

Photochromic properties of composite films of thermally irreversible diarylethenes and fulgimides in polytetrafluoroethylene matrix

“…This paper is devoted to application of the above mentioned method for preparation of composite films based on PTFE and thermally irreversible photochromic compounds from diarylethene [3] and fulgimide [4] classes and researches of their properties. These photochromic compounds are of interest for development of 3D optical memory [5].…”

Study of functional properties of thermally irreversible photochromic diarylethenes in various aggregate states

“…Throughout last few years study of functional properties of photochromic diarylethenes have been in a focus of considerable interest from the viewpoint of possible application as components for photochromic reversible recording media for 3D bitwise working optical memory [1,2]. It is well known, that such compounds undergo photoinduced reversible valence isomerisation between open-(A) and closed-ring (B) form isomers:…”